David Rothkopf is CEO and editor at large of Foreign Policy.

It is easy to be skeptical when the alarms start going off about a pending Israeli attack on Iran. They seem to come with the seasons, a geopolitical biorhythm that reminds us never to be too comfortable with one of the world's most volatile relationships. But it is worth remembering that the punch line of the story about the little boy who cried wolf is that ultimately, the wolf shows up.

For all the good reasons Israel might want to show forbearance, seven of which were pointed out by the Atlantic's Jeffrey Goldberg recently, the reasons to attack are also clearly growing more compelling for Israeli leaders, uniting them on this issue to a greater degree than at any time in the recent past. Diplomacy doesn't seem to be working. The Iranian nuclear program continues moving closer to weapons capability. And the Iranians themselves have matched their rhetoric about the annihilation of Israel with direct support for attacks on its people, like the suicide-bomb murder of five Israeli tourists in Bulgaria, which U.S. officials have linked to Iran.

It is often hard for Americans to grasp the idea of an existential threat to a nation. While one existed for Americans during the Cold War, since then the notion that any single actor with any single act could effectively obliterate Americans or their lifestyle is very hard for many people to get their brains around. But that is exactly the threat that Israelis face from even a "limited" Iranian nuclear attack. And though it is reasonable to debate whether the Iranians would actually use such a weapon against Israel given the likely consequences for them, from the Israeli perspective, given Iranian threats and actions, the risks of guessing wrong about the intent of the leaders in Tehran are so high that inaction could easily be seen to be the imprudent path.

This summarizes the carefully worded case made last week in the Wall Street Journal by Israel's ambassador to the United States, Michael Oren...